CN107910197B - Lithium ion capacitor and preparation method thereof - Google Patents
Lithium ion capacitor and preparation method thereof Download PDFInfo
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- CN107910197B CN107910197B CN201710895378.6A CN201710895378A CN107910197B CN 107910197 B CN107910197 B CN 107910197B CN 201710895378 A CN201710895378 A CN 201710895378A CN 107910197 B CN107910197 B CN 107910197B
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 55
- 239000003990 capacitor Substances 0.000 title claims abstract description 51
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000007774 positive electrode material Substances 0.000 claims abstract description 17
- 229910010648 Li6CoO4 Inorganic materials 0.000 claims abstract description 13
- 229910052493 LiFePO4 Inorganic materials 0.000 claims abstract description 13
- 229910012742 LiNi0.5Co0.3Mn0.2O2 Inorganic materials 0.000 claims abstract description 10
- 229910052799 carbon Inorganic materials 0.000 claims abstract 4
- 239000007773 negative electrode material Substances 0.000 claims description 24
- 239000006258 conductive agent Substances 0.000 claims description 22
- 239000011883 electrode binding agent Substances 0.000 claims description 19
- 238000001035 drying Methods 0.000 claims description 14
- 239000002270 dispersing agent Substances 0.000 claims description 13
- 239000006185 dispersion Substances 0.000 claims description 13
- 238000003756 stirring Methods 0.000 claims description 13
- 238000000576 coating method Methods 0.000 claims description 12
- 239000011267 electrode slurry Substances 0.000 claims description 12
- 229910021385 hard carbon Inorganic materials 0.000 claims description 11
- 238000005096 rolling process Methods 0.000 claims description 10
- 229910021384 soft carbon Inorganic materials 0.000 claims description 10
- 239000011248 coating agent Substances 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Natural products OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 238000004080 punching Methods 0.000 claims description 6
- 229910010710 LiFePO Inorganic materials 0.000 claims description 5
- -1 citric acid ester Chemical class 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 239000002131 composite material Substances 0.000 claims description 3
- 239000008367 deionised water Substances 0.000 claims description 3
- 229910021641 deionized water Inorganic materials 0.000 claims description 3
- 238000003475 lamination Methods 0.000 claims description 3
- 238000004806 packaging method and process Methods 0.000 claims description 3
- 239000004005 microsphere Substances 0.000 claims 2
- 238000004146 energy storage Methods 0.000 abstract description 4
- 238000000034 method Methods 0.000 description 20
- 229910052744 lithium Inorganic materials 0.000 description 17
- 239000003792 electrolyte Substances 0.000 description 15
- 239000011888 foil Substances 0.000 description 15
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 14
- 230000007797 corrosion Effects 0.000 description 8
- 238000005260 corrosion Methods 0.000 description 8
- 239000002931 mesocarbon microbead Substances 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 239000003960 organic solvent Substances 0.000 description 7
- 229910000831 Steel Inorganic materials 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 229910001220 stainless steel Inorganic materials 0.000 description 6
- 239000010935 stainless steel Substances 0.000 description 6
- 239000010959 steel Substances 0.000 description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 5
- 239000011149 active material Substances 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- 239000011889 copper foil Substances 0.000 description 5
- 239000002033 PVDF binder Substances 0.000 description 4
- 239000010405 anode material Substances 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 4
- 239000003575 carbonaceous material Substances 0.000 description 4
- 230000002687 intercalation Effects 0.000 description 4
- 238000009830 intercalation Methods 0.000 description 4
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 4
- 239000004810 polytetrafluoroethylene Substances 0.000 description 4
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 4
- 238000007086 side reaction Methods 0.000 description 4
- 238000009210 therapy by ultrasound Methods 0.000 description 4
- 239000001768 carboxy methyl cellulose Substances 0.000 description 3
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 3
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 3
- 239000010406 cathode material Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 230000002195 synergetic effect Effects 0.000 description 3
- 239000004925 Acrylic resin Substances 0.000 description 2
- 229920000178 Acrylic resin Polymers 0.000 description 2
- 229910015645 LiMn Inorganic materials 0.000 description 2
- 229910013716 LiNi Inorganic materials 0.000 description 2
- 229910001290 LiPF6 Inorganic materials 0.000 description 2
- 239000006183 anode active material Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000002041 carbon nanotube Substances 0.000 description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 description 2
- 238000009831 deintercalation Methods 0.000 description 2
- 229910021389 graphene Inorganic materials 0.000 description 2
- 239000011357 graphitized carbon fiber Substances 0.000 description 2
- 238000009775 high-speed stirring Methods 0.000 description 2
- 230000002427 irreversible effect Effects 0.000 description 2
- 229910001486 lithium perchlorate Inorganic materials 0.000 description 2
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229910021382 natural graphite Inorganic materials 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 238000006479 redox reaction Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 description 2
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical group C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 description 1
- 229910015872 LiNi0.8Co0.1Mn0.1O2 Inorganic materials 0.000 description 1
- 235000010724 Wisteria floribunda Nutrition 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000006182 cathode active material Substances 0.000 description 1
- 239000006257 cathode slurry Substances 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/66—Current collectors
- H01G11/68—Current collectors characterised by their material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/04—Hybrid capacitors
- H01G11/06—Hybrid capacitors with one of the electrodes allowing ions to be reversibly doped thereinto, e.g. lithium ion capacitors [LIC]
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/46—Metal oxides
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Electric Double-Layer Capacitors Or The Like (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention relates to a lithium ion capacitor and a preparation method thereof, and belongs to the technical field of new energy storage. The positive electrode of the lithium ion capacitor comprises a positive electrode current collector and a positive electrode active material coated on the positive electrode current collector, wherein the positive electrode active material comprises active carbon and LiFePO4、LiNi0.5Co0.3Mn0.2O2And Li6CoO4. The lithium ion capacitor disclosed by the invention is simple in preparation process and high in energy density.
Description
Technical Field
The invention belongs to the technical field of new energy storage, and relates to a lithium ion capacitor and a preparation method thereof.
Background
With the development of science and technology, various energy storage devices are greatly developed. The lithium ion capacitor is used as a novel energy storage device between the super capacitor and the lithium ion battery, has the advantages of high energy density, high power density and ultra-long cycle life, and is expected to be widely applied to the fields of new energy automobiles, solar energy, wind energy, military industry and aerospace and the like.
The negative electrode of the lithium ion capacitor adopts carbon materials (such as graphite, soft carbon and hard carbon) capable of releasing and embedding lithium ions, the defect of high self-discharge rate of a common super capacitor is overcome, and the positive electrode adopts carbon materials (such as activated carbon) capable of physically and chemically adsorbing lithium ions, so that the use working condition of large-current discharge can be considered. However, since the positive and negative electrodes of the lithium ion capacitor do not contain lithium ions, it is necessary to add lithium ions to the capacitor in advance.
Currently, a method disclosed in patent CN200580004509.2 of fuji heavy industry co is mainly used to manufacture a lithium ion capacitor, in which lithium metal is used as a lithium source, a porous copper foil (negative electrode) and a porous aluminum foil (positive electrode) are used as current collectors, and lithium ions are inserted into a negative electrode active material by an electrochemical contact method, so that a high-capacity power storage device with high energy density is obtained, and the high-capacity power storage device has good charge and discharge characteristics. However, in the preparation process of the product, the lithium metal has extremely active chemical properties, is unsafe and has extremely high requirements on the environment; secondly, the lithium embedding amount is accurately controlled due to the requirement of the lithium pre-embedding process, so that the accurate amount control requirement is difficult to meet by adopting a metal lithium sheet as a lithium source; moreover, when a porous metal current collector is used, the material coating process is complex, so that the lithium ion capacitor is not enough in industrialization degree and has a high price. Therefore, there is a need to develop a novel lithium ion capacitor with a simple manufacturing process and high energy density.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides a lithium ion capacitor with simple preparation process and high energy density.
The purpose of the invention can be realized by the following technical scheme:
the lithium ion capacitor comprises a positive electrode and a negative electrode, and is characterized in that the positive electrode comprises a positive electrode current collector and a positive electrode active material coated on the positive electrode current collector, and the positive electrode active material comprises activated carbon and LiFePO (lithium iron phosphate)4、LiNi0.5Co0.3Mn0.2O2And Li6CoO4。
The components and mass percentages of the anode active material and the cathode active material are reasonably proportioned, so that the side reaction of the anode active material is effectively reduced, the performance and the service life of the capacitor are improved, and the safety in the preparation process is improved. LiFePO4The theoretical discharge capacity is high and can reach 170 mA.h, and the ordered olivine structure can keep the lattice stable after the lithium ions are de-intercalated, so that LiFePO4The lithium ion capacitor can effectively improve the stability of the lithium ion capacitor when used as the anode. In addition, in the charge-discharge cycle process of the lithium ion capacitor, a large amount of side reactions are easy to occur on the anode material in a high-voltage state for a long time, so that the electrode material is peeled off and lost, the service life is shortened, and LiNi with a wider voltage range is introduced0.5Co0.3Mn0.2O2(NCM) with LiFePO4And under the synergistic effect, partial voltage is shared under a high-voltage state, the loss of the anode material is reduced, and the cycle life is prolonged.
Metal oxide Li6CoO4The capacity is high, irreversible redox reaction of lithium ion deintercalation is easy to occur, so that the lithium ions are rapidly and stably intercalated into the negative electrode, active metal lithium is not required to be introduced in the lithium intercalation process of the lithium ions, and the safety and reliability in the preparation process of the lithium ion capacitor are greatly improvedAnd (4) sex. In the invention, Li6CoO4The content of (A) is controlled within 5-20%, such as Li6CoO4On one hand, the content is too high, so that the precipitation of lithium metal is easily caused in the process of pre-embedding lithium, the cycle life of the lithium ion capacitor is seriously shortened, and meanwhile, the safety of the lithium ion capacitor in the use process cannot be guaranteed; on the other hand, too much Li6CoO4Can not be completely consumed in the process of pre-lithium intercalation, can not play a role in the subsequent use process to cause waste, and reduces the specific energy of the whole system. Li6CoO4When the content is too low, the negative electrode cannot sufficiently complete the lithium intercalation process, resulting in a decrease in energy density of the entire system of the lithium ion capacitor.
Preferably, the LiFePO4And LiNi0.5Co0.3Mn0.2O2The mass ratio of (A) to (B) is 1: 4-3: 2.
According to the invention, the ratio of LFP to NCM is controlled within the range of 1: 4-3: 2, and the LFP and the NCM form a good synergistic effect, so that the energy density and the cycle life of the lithium ion capacitor are effectively improved. When the ratio of LFP to NCM is less than 1:4, the energy density of the lithium ion capacitor can be obviously improved, but the cycle life of the whole system can be reduced; when the ratio of LFP to NCM is greater than 3:2, the probability of side reaction of the positive electrode active carbon material in a high-voltage state is increased, the possibility of the active material peeling is improved, and the performance and the service life of the lithium ion capacitor are reduced.
Preferably, the negative electrode comprises a negative electrode current collector and a negative electrode active material coated on the negative electrode current collector, wherein the negative electrode active material comprises one or more of soft carbon, mesocarbon microbeads, hard carbon and natural graphite.
Preferably, the negative active material is a composite of soft carbon, mesocarbon microbeads and hard carbon, and the mass ratio of the soft carbon to the mesocarbon microbeads to the hard carbon is 100 (8-15) to (9-20).
According to the invention, the mesocarbon microbeads and the hard carbon are used as the negative active materials in a matching manner on the basis of the soft carbon, and the mass ratio of the mesocarbon microbeads to the hard carbon is controlled within the range so as to obtain the optimal synergistic effect, so that the specific capacity of the lithium ion capacitor is effectively improved and the service life is prolonged on the premise of controlling the cost of the negative material.
Preferably, the positive electrode current collector is a corrosion aluminum foil or a stainless steel foil, and more preferably a non-porous corrosion aluminum foil or a non-porous stainless steel foil; the negative current collector is a corrosion copper foil or a stainless steel foil, and is preferably a non-porous corrosion copper foil or a non-porous stainless steel foil.
Compared with the porous metal foil, the invention has the advantages of simple operation, reduced manufacturing cost and easy realization of industrialization. On the other hand, fine concave parts exist on the surface of the corrosion metal foil, and in the coating and rolling process of the active material, the active material is easily embedded into the concave parts and is connected with the active substance on the surface of the metal foil to form a continuous coating layer, so that the adhesion between the active material and the surface of the corrosion metal foil is improved.
Preferably, the thickness of the positive electrode sheet is 200 to 240 μm, and the thickness of the negative electrode sheet is 80 to 110 μm.
In the present invention, if the positive electrode sheet is too thick, the active material is likely to peel off to affect the cycle stability of the capacitor, and if it is too thin, the theoretical capacity of the negative electrode material cannot be sufficiently exhibited, resulting in a decrease in the capacity per unit volume of the device. If the negative electrode is too thick, the capacity of the negative electrode becomes too large to be actually used. In addition, the thickness of the negative plate is lower than that of the positive plate, so that the specific capacity of the negative electrode is larger than that of the positive electrode, better capacity matching is formed by the positive and negative electrode materials,
preferably, the positive electrode further comprises a positive conductive agent and a positive binder coated on the positive current collector, the negative electrode further comprises a negative conductive agent, a negative binder and a dispersing agent coated on the positive current collector, and the positive conductive agent and the negative conductive agent are one or more of conductive carbon black, carbon nanotubes, graphitized carbon fibers and graphene.
Preferably, the positive binder is one or more of acrylic resin and polyvinylidene fluoride (PVDF). The negative electrode binder is one or more of Polytetrafluoroethylene (PTFE), Styrene Butadiene Rubber (SBR) and LA 123.
Preferably, the dispersant in step S2 is a mixture of carboxymethyl cellulose (CMC) and citrate, and the mass ratio of the CMC to the citrate is 100 (5.5-8.5).
According to the invention, a small amount of citrate is added into CMC to be used as a dispersing agent, active groups of the citrate can be connected with active groups on the surface of a negative electrode active material, and isolation is formed between the negative electrode active materials, so that the dispersibility of the negative electrode active material is improved, but the capacitor capacity is reduced due to the excessive content of the citrate.
Wherein, LA123 is a code of a water-based binder, and the main component is acrylonitrile multipolymer which has excellent binding performance.
Preferably, the lithium ion capacitor further comprises an electrolyte and an electrolyte, wherein the electrolyte comprises an organic solvent and an electrolyte dissolved in the organic solvent, the organic solvent is one or more of EMC, EC, DEC and DMC, and the electrolyte is LiPF6、LiBF4、LiClO4One or more of them.
Another object of the present invention is to provide a method for preparing a lithium ion capacitor, the method comprising the steps of:
s1, mixing activated carbon and LiFePO4、NCM、Li6CoO4Mixing a positive electrode conductive agent and a positive electrode binder in N-methyl pyrrolidone (NMP), performing vacuum high-speed dispersion treatment to obtain positive electrode slurry, coating the positive electrode slurry on the front and back surfaces of a positive electrode current collector, and drying, rolling and punching to obtain a positive electrode plate;
and S2, mixing the negative electrode active material, the negative electrode conductive agent, the negative electrode binder and the dispersing agent in deionized water, and performing high-speed vacuum dispersion treatment to obtain negative electrode slurry. Coating the negative electrode slurry on the front and back surfaces of a negative electrode current collector, and drying, rolling and punching to obtain a negative electrode plate;
and S3, manufacturing the positive plate, the diaphragm and the negative plate into a battery cell in a Z-shaped lamination mode, and drying, injecting liquid and packaging to obtain the lithium ion capacitor.
The invention disperses the anode and cathode materials at high speed in vacuum environment, can mix the anode and cathode materials uniformly with high efficiency without layering, and avoids the increase of the internal resistance of the capacitor caused by the entering of air and the generation of bubbles.
Preferably, in the step S1, the mass percentages of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder are respectively 30-60% of activated carbon and 15-50% (LiFePO)4+LiNi0.5Co0.3Mn0.2O2)，5～20％Li6CoO43-8% of positive electrode conductive agent and 5-12% of positive electrode binder.
Preferably, the vacuum pressure during the vacuum high-speed dispersion treatment in the step S1 is-0.03 MPa to-0.1 MPa, the stirring speed is 8000 to 10000r/min, and the stirring time is 4 to 6 hours.
Preferably, in step S2, the negative electrode active material, the negative electrode conductive agent, the negative electrode binder, and the dispersing agent are respectively in the following mass percentages: 88-92% of a negative electrode active material, 3-7% of a negative electrode conductive agent, 1-3% of a negative electrode binder and 1-3% of a dispersing agent.
Preferably, the vacuum pressure during the vacuum high-speed dispersion treatment in the step S2 is-0.03 MPa to-0.1 MPa, the stirring speed is 8000 to 10000r/min, and the stirring time is 4 to 6 hours.
Preferably, ultrasonic treatment with a power of 500w is performed simultaneously during the vacuum high-speed dispersion treatment in steps S1 and S2.
The ultrasonic treatment is beneficial to the uniformity of dispersion, and can destroy bubbles possibly generated in the stirring process, thereby improving the formation quality of the anode slurry and the cathode slurry.
Compared with the prior art, the invention has the following beneficial effects:
(1) by introducing into the positive electrode material a metal oxide Li having a high capacity and susceptible to irreversible redox reactions in which the lithium ion deintercalation process occurs6CoO4Finally, the lithium ions are successfully inserted into the negative electrode, and active metal lithium is not required to be introduced in the lithium inserting process, so that the safety and reliability in the manufacturing process are greatly improved.
(2) By NCM, LiFePO4The introduction of the method improves the capacity of the lithium ion capacitor, reduces the side reaction of the anode active carbon material in the circulation process and obviously improves the cycle life of the product.
(3) In the preparation process of the lithium ion capacitor electrode, porous aluminum foil and copper foil are not needed, the production cost is low, the operation is simple and controllable, and the industrial production is easy to realize.
Detailed Description
The following are specific examples of the present invention and further describe the technical solutions of the present invention, but the present invention is not limited to these examples.
Examples 1 to 5
The lithium ion capacitor in examples 1 to 5 includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, the positive electrode sheet, the negative electrode sheet and the separator are immersed in the electrolyte,
the thickness of the positive plate is 200-240 mu m, the positive plate comprises a positive current collector and a positive material coated on the positive current collector, the positive current collector is a non-porous corrosion aluminum foil or a non-porous stainless steel foil, the positive material comprises the following components in percentage by mass,
activated carbon: 30 to 60 percent of the total weight of the steel,
LiFePO4+NCM：15～50％，
Li6CoO4：5～20％，
positive electrode conductive agent: 3 to 8 percent of the total weight of the steel,
positive electrode binder: 5 to 12 percent of the total weight of the steel,
LiFePO4and LiNi0.5Co0.3Mn0.2O2The mass ratio of (A) to (B) is 1: 4-3: 2.
The thickness of the negative plate is 80-110 μm, the negative plate comprises a positive current collector and a negative material coated on the negative current collector, the negative current collector is a non-porous corrosion copper foil or a non-porous stainless steel foil, the negative material comprises the following components in percentage by mass,
negative electrode active material: 88 to 92 percent of the total weight of the steel,
negative electrode conductive agent: 3 to 7 percent of the total weight of the steel,
and (3) a negative electrode binder: 1 to 5 percent of the total weight of the steel,
dispersing agent: 1 to 3 percent of the total amount of the catalyst,
the negative active material is one or more of natural graphite, hard carbon, soft carbon and mesocarbon microbeads, preferably a composite of the soft carbon, the mesocarbon microbeads and the hard carbon, and the mass ratio of the soft carbon to the mesocarbon microbeads to the hard carbon is (8-15) to (9-20).
The positive electrode conductive agent and the negative electrode conductive agent are one or more of conductive carbon black, carbon nano tubes, graphitized carbon fibers and graphene.
The positive electrode binder is one or more of acrylic resin and polyvinylidene fluoride (PVDF). The negative electrode binder is one or more of Polytetrafluoroethylene (PTFE), Styrene Butadiene Rubber (SBR) and LA 123.
The dispersing agent is a mixture of carboxymethyl cellulose (CMC) and citric acid ester, and the mass ratio of the CMC to the citric acid ester is 100 (5.5-8.5).
The electrolyte comprises an organic solvent and an electrolyte dissolved in the organic solvent, wherein the organic solvent is one or more of EMC, EC, DEC and DMC, and the electrolyte is LiPF6、 LiBF4、LiClO4One or more of them.
The components and contents of the positive and negative electrode materials, the electrolyte, and the separator in examples 1 to 5 are shown in tables 1 to 3.
Table 1: components and contents of the cathode materials in examples 1 to 5
Table 2: components and contents of the negative electrode materials in examples 1 to 5
Table 3: components and contents of electrolyte and separator in examples 1 to 5
Examples 6 to 10
The preparation method of the lithium ion capacitor in the embodiment 6-10 comprises the following steps:
(1) preparing raw materials: raw materials were prepared according to the components and contents in example 1;
(2) and preparing a positive plate: mixing activated carbon and LiFePO4、NCM、Li6CoO4Dissolving a positive electrode conductive agent and a positive electrode binder in NMP in sequence, stirring for 4-6 h at a stirring speed of 8000-10000 r/min under a vacuum pressure of-0.03-0.1 MPa by using high-speed stirring equipment to form uniform positive electrode slurry, performing ultrasonic treatment with the power of 500w simultaneously in the vacuum high-speed dispersion treatment process, coating the positive electrode slurry on the front and back surfaces of a positive electrode current collector, performing stepped drying while coating, wherein a drying system consists of a plurality of drying boxes with different temperatures, the temperatures are respectively set to be 120 ℃, 130 ℃, 140 ℃, 135 ℃, 130 ℃ and 125 ℃, the thickness of a positive electrode sheet in the coating process is controlled to be 220-265 mu m, rolling the dried positive electrode sheet, and controlling the thickness of the positive electrode sheet to be 200-240 mu m after rolling, and then obtaining the positive electrode sheet with the thickness of 55mm 75 mm;
(3) and preparing a negative plate: dissolving a negative electrode active material, a negative electrode conductive agent, a negative electrode binder and a dispersing agent in deionized water in sequence, stirring for 4-6 h at a stirring speed of 8000-10000 r/min under a vacuum pressure of-0.03-0.1 MPa by using high-speed stirring equipment to perform vacuum high-speed dispersion treatment to form uniform negative electrode slurry, simultaneously performing ultrasonic treatment with the power of 500w in the vacuum high-speed dispersion treatment process, coating the negative electrode slurry on the front and back surfaces of a negative electrode current collector, performing stepped drying while coating, wherein a drying system comprises a plurality of drying boxes with different temperatures, the temperatures are respectively set to be 120 ℃, 130 ℃, 140 ℃, 130 ℃ and 125 ℃, the thickness of a negative electrode sheet in the coating process is controlled to be 90-130 mu m, rolling the dried negative electrode sheet, controlling the thickness of the negative electrode sheet to be 80-100 mu m after rolling, and then punching to obtain a negative electrode sheet with the thickness of 55mm 75mm, drying, rolling and punching to obtain a negative plate;
(4) and preparing a capacitor: separating the positive pole piece and the negative pole piece by using a cellulose paper diaphragm, manufacturing a battery cell in a Z-shaped lamination mode, drying the battery cell in vacuum at 145-155 ℃ for 18-22 h, dissolving electrolyte into an organic solvent to prepare electrolyte, injecting the electrolyte into the battery cell in a glove box, packaging the battery cell in an aluminum-plastic film, standing for 10-14 h to obtain a lithium ion capacitor, then charging to 4.1V under the condition of 0.05C, and stabilizing the voltage for 8h to obtain the lithium ion capacitor completing the pre-lithium intercalation process.
Specific parameters of each step in examples 6 to 10 are shown in Table 4.
Table 4: parameters of the respective steps in examples 6 to 10
Examples 11 to 14
Raw materials were prepared according to the compositions and contents of examples 2 to 5, respectively, and a lithium ion capacitor was produced according to the production method in example 6.
Comparative example 1
Use of metallic lithium in place of Li in positive electrode material6CoO4Otherwise, the same as example 6.
Comparative example 2
Use of LiMn in positive electrode material2O4Instead of LiFePO4Otherwise, the same as example 6.
Comparative example 3
LiNi was used as a positive electrode material0.8Co0.1Mn0.1O2In place of LiNi0.5Co0.3Mn0.2O2Otherwise, the same as example 6.
Comparative example 4
LiMn is used in the positive electrode material2O4Instead of LiFePO4Using LiNi0.8Co0.1Mn0.1O2In place of LiNi0.5Co0.3Mn0.2O2Otherwise, the same as example 6.
Comparative example 5
Conventional lithium ion capacitors.
The performance of the lithium ion capacitors prepared in examples 6 to 14 of the present invention and comparative examples 1 to 4 were compared, and the comparison results are shown in table 5, where the capacity retention ratio was measured after 10000 cycles under the condition of 3A/g current density, and the specific energy was measured under the condition of 1A/g current density.
Table 5: performance of lithium ion capacitors in examples 6 to 14 and comparative examples 1 to 5
In conclusion, the performance and the safety of the lithium ion capacitor are effectively improved by reasonably matching the components and the mass percentages of the positive and negative electrode materials.
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
Claims (5)
1. The preparation method of the lithium ion capacitor is characterized in that the lithium ion capacitor comprises a positive electrode and a negative electrode, the positive electrode comprises a positive electrode current collector and a positive electrode active material coated on the positive electrode current collector, and the positive electrode active material comprises active carbon and LiFePO (LiFePO)4、LiNi0.5Co0.3Mn0.2O2And Li6CoO4Said LiFePO4And LiNi0.5Co0.3Mn0.2O2The mass ratio of (A) to (B) is 1: 4-3: 2;
the negative electrode comprises a negative electrode current collector and a negative electrode active material coated on the negative electrode current collector, wherein the negative electrode active material is a composite of soft carbon, intermediate phase carbon microspheres and hard carbon, and the mass ratio of the soft carbon to the intermediate phase carbon microspheres to the hard carbon is 100 (8-15) to (9-20);
the preparation method of the lithium ion capacitor comprises the following steps:
s1, mixing the positive electrode active material, the positive electrode conductive agent and the positive electrode binder in N-methyl pyrrolidone, performing vacuum high-speed dispersion treatment to obtain positive electrode slurry, coating the positive electrode slurry on the front and back surfaces of a positive electrode current collector, and drying, rolling and punching to obtain a positive electrode;
s2, mixing a negative electrode active material, a negative electrode conductive agent, a negative electrode binder and a dispersing agent in deionized water, carrying out vacuum high-speed dispersion treatment for 4-6 h to obtain negative electrode slurry, coating the negative electrode slurry on the front and back surfaces of a negative electrode current collector, and drying, rolling and punching to obtain a negative electrode; the dispersing agent is a mixture of carboxymethyl cellulose (CMC) and citric acid ester in a mass ratio of 100 (5.5-8.5);
and S3, manufacturing the positive electrode, the diaphragm and the negative electrode into a battery cell in a Z-shaped lamination mode, and drying, injecting and packaging to obtain the lithium ion capacitor.
2. The preparation method according to claim 1, wherein the mass percentages of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder in the step S1 are respectively 30-60% of activated carbon and 15-50% (LiFePO)4+LiNi0.5Co0.3Mn0.2O2），5~20% Li6CoO43-8% of positive electrode conductive agent and 5-12% of positive electrode binder.
3. The preparation method according to claim 1, wherein the vacuum degree of the vacuum high-speed dispersion treatment in the step S1 is-0.03 to-0.1 MPa, the stirring speed is 8000 to 10000r/min, and the stirring time is 4 to 6 hours.
4. The preparation method according to claim 1, wherein the mass percentages of the negative electrode active material, the negative electrode conductive agent, the negative electrode binder and the dispersing agent in the step S2 are respectively as follows: 88-92% of a negative electrode active material, 3-7% of a negative electrode conductive agent, 1-3% of a negative electrode binder and 1-3% of a dispersing agent.
5. The preparation method according to claim 1, wherein the vacuum degree of the vacuum high-speed dispersion treatment in the step S2 is-0.03 to-0.1 MPa, the stirring speed is 8000 to 10000r/min, and the stirring time is 4 to 6 hours.
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